#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
#    Code base of Animesh Sharma [ sharma.animesh@gmail.com ]

$f=@ARGV[0];#scanf

$c=fact($f);
print "$c\n";

sub fact {
	my ($n) = shift;
	if($n ==1 || $n == 0){return 1;}
	else
	{
		$p = fact($n-1);
		return ($n*$p);
	}
}
#$m=$f*30;print "$m\n"